Andean soils keep carbon out of the atmosphere

Very large carbon pools are locked up in the threatened peatlands and wet grasslands of the AndesCIP

Global efforts and agreements against climate change have long concentrated on the role of forests as carbon sinks, while overlooking the importance of soil. The world's soils actually hold far more trapped carbon than plants, and some farming practices can threaten their holding capacity, releasing carbon into the atmosphere and furthering climate change. In the Andes Mountains of Peru, scientists at the International Potato Center (CIP) and their Brazilian partners have employed advanced tests to more precisely understand the role of soils in the carbon cycle, and how they are being affected by human activity.

A mountain storehouse

Farmers in Peru are confronting the effects of climate change, with rising temperatures bringing more damaging droughts, pests and diseases. As the farmers respond by moving their potatoes and other crops to even higher altitudes in the Andes, they unwittingly worsen the problem by releasing more soil carbon from beneath highland ecosystems.

Researchers at CIP have found that the highland areas of wet grasslands and peatlands, locally called páramos and bofedales, hold exceptionally large carbon stores. "If you have a place that is waterlogged, there is no exchange with the atmosphere, no oxygen, so decomposition slows down a bit, keeping the carbon trapped underground," explains Roberto Quiroz, leader of CIP's Natural Resources Management Division. CIP's measurements have shown that the upward climb of agriculture has impacted these areas, and farmers' ploughs and livestock may have a significant impact on climate change.

Climate change is driving Andean farmers to establish new fields at higher altitudesCIP

Environments such as the páramos and bofedales of the Andes should stand among the planet's important and threatened carbon sinks, but if they are to draw attention, their value to the global carbon cycle must be quantified. The data must include both measurements of their total carbon stocks, and the recalcitrance of the carbon, or how tightly it is bound up in the soil. CIP teamed up with the Brazilian Agricultural Research Corporation and the University of Sao Paulo to use electron paramagnetic resonance (EPR) in the lab and portable laser-induced fluorescence (LIF) in the field, two advanced methods for measuring and identifying carbon content in soil samples.

Quantifying carbon

The soils analysed were sampled from the coast, high Andean plateau, and the eastern hillsides in the south of Peru, a range of locations spanning five major agro-ecologies and a wide range of cultivation practices. The researchers confirmed that the soils of the wet grasslands and peatlands are the most substantial carbon sinks, storing far more carbon than soil under crops and even under undisturbed rainforest. They also found that these soils are some of the least recalcitrant, meaning the carbon exists in small molecules and is easily released if the soil is ploughed.

Unfortunately, as the changing climate of the Andes drives farmers to cultivate higher land, these are the ecosystems facing disruption. The researchers estimate that bringing a hectare of wet grassland into potato cultivation could cause an emission of over 200 tonnes of carbon.

These impacts can be limited with farming methods which minimise ploughing, increase mulching, and better manage crops and water to keep carbon in the soil. Better adapted crops with greater resilience to climate change can also help by making it possible for farmers to keep planting in lower altitudes. CIP is already working on developing greater resistance to heat, drought and pests in potatoes and sweet potatoes.

Global tools

Ploughing soil, as here in Peru, can release large quantities of stored carbon into the atmosphereCIP

CIP hopes the outputs of this project will be relevant to more than just Peru's farmers. "The goal is to establish a standard acceptable procedure, so anyone can go and measure to see if their agricultural practices are affecting the carbon pool in the soil," Quiroz says. "These devices for field measurements will be defined, and the private sector will probably build these as commercial equipment for field measurement."

Quiroz's team is already moving on to try out soil carbon evaluations elsewhere. "We just covered a transect on Mount Kenya in all of the agricultural and pasture lands, and the plan for 2011 is to do something in China," he reports. They have also been asked to bring the methodology to the World Bank, which wants to incorporate the measurements into a pilot project for payment to farmers for environmental services in conserving carbon in peat lands and grasslands.

"The carbon sink in the soil is much larger than that of plants or even the earth's atmosphere," Quiroz points out, "and we need to put resources into quantifying this and having the methodology ready so people can be conscious about what their practices are doing to the carbon sink in the soil."